Energy absorption behavior and damage constitutive model of frozen moraine soil under impact loading

Frozen moraine soils are widely distributed across the Tianshan Mountains, the Qinghai-Tibetan Plateau, and other high-altitude regions. Engineering activities, particularly blasting, often induce degradation of the soil microstructure, compromising its mechanical integrity and increasing the risk of slope instability and rainfall-triggered debris flows—posing serious threats to infrastructure in cold regions. Previous studies have largely treated frozen soils as homogeneous continua, thereby overlooking key micro-scale processes such as ice–soil interaction, microcrack propagation, and particle breakage. In this study, the dynamic mechanical behavior and microstructural damage mechanisms of frozen moraine soil were systematically investigated under varying temperatures (−5 ℃, −15 ℃, and −25 ℃) and strain rates (50 s^-1, 70 s^-1, and 90 s^-1). Results reveal that both temperature and strain rate significantly influence the dynamic stress–strain response. Energy absorption exhibits a three-stage pattern of increase, stabilization, and decline. At −25℃, increased ice brittleness reduces the peak energy absorption efficiency under impact. To capture the observed nonlinear behavior, a damage-based constitutive model was developed, incorporating coupled effects of impact-induced microcracking, ice–soil interfacial debonding, and particle fracture. The stochastic evolution of interfacial debonding and grain breakage was described using a Weibull statistical framework, linking microstructural deterioration to macroscopic response. The model shows strong agreement with experimental data and accurately simulates key parameters such as peak stress and energy absorption. These findings enhance the understanding of dynamic damage mechanisms in frozen soils and offer a computational tool for the safety assessment and hazard mitigation of engineering structures in cold, high-altitude environments.